Pistons for internal combustion engines



Dec. 3, 1957 G. A. HOLT PISTONS FOR INTERNAL COMBUSTION ENGINES 5 Sheets-Sheet 1 Filed Aug. e 1956 INVENTQE GEORGE A. Hour A ATTORN EYs Dec. 3, 1957 G. A. HOLT PISTONS FOR INTERNAL COMBUSTION ENGINES Aug. 6,1956

3 Sheets-Sheet 2 FIG. 4.-

INVENTOR GEGRGE A. Holrr BY pm m ATTORNEY? Dec. 3, 1957 G. A. HOLT 2,815,011

PISTONS FOR INTERNAL COMBUSTION ENGINES Filed Aug. 6, 1956 3 Sheets-Sheet 3 INVENTOR GEORGE. A. Hon-r BY WM, 64, 1 WW AT ToI zN E13 1 PISTONS EQRINTERNAL COMBUSTION ENGINES y George Allen Holt,; Shoreham-by-Sea;:England, assignor to Ricardo 8r (lo aEngineers (1927) Limited, London, England, a. British company ApplicationAugust 6, 195 6, SerialNo. 602,201

Claims priority, epplic ation Great Britain August 22, 1955 5 8 Claims. .(Cl. 123-4138) gudgeon pinbossesand the crown during operation of the piston, which oilis shakenbaek and forth by the reciprocaition of the piston, and is replenished by a jet from a I nozzle carriedbythe connecting rod and directed through -.an. aperture-into-the space referred to while surplus oil is ejected from the spacetowards the end of each outstroke \of therpiston-through the same aperture or one or more other passages.

:Examples of-trunkpistonsof the kind referred to are described in the specifications of the present applicants Us 8.. Patent No. 2,523,699.

It is an object of the present invention to provide an improved form of trunkpi-ston-of the kind referred to which will facilitate manufacture and/or have other 1 advantages.

A trunk piston assembly according to the present invention for. anuinternal combustion engine comprises a .piston bodylincluding a crown from which projects a ring- .carrying and skirt portion provided with gudgeon pin bosses or the like, and a self-contained trough member secured within thexpiston element so as to be spaced from :the crown and lie-above the gudgeon pin bosses, which trough memberuis of annular form and comprises an annular base and inner and outer side walls projecting from the base towards the crown to provide a trough which will retain a quantity of oil, and surrounds an aperture, herein called the central aperture, through which oil can be fed into the space between the trough and the crown from a nozzle on the connecting rod.

For convenience herein it will be assumed that the pistonlis arranged with its axis vertical and its crown at the top but the invention is applicable to pistons otherwise disposed where, as is usually the case the normal speeds of operation are such that gravity effects can be ignored.

The quantity of oil which, during operation of the piston, will be retained and shaken back and forth in the space between the trough member and the crown depends upon the formation of the piston crown and of the trough member and as will be understood will in any instance be that which provides for the ejection from the space during each complete reciprocation of the piston of just that quantity of oil which is delivered during such reciprocation into the space.

In a piston assembly according to the present invention the arrangement may be such that the ejection of oil from the space takes place substantially wholly through the central aperture, substantially wholly through ejection passages opening at an appropriate level in the trough and extending away from the crown to ejection apertures below the trough, or substantially wholly through one or more apertures between the outer sidewall of the trough 2,815,011 gPatented Dec. 3, ,1 957 and the adjacent parts of.the piston element or partly in .each of two ormore of these ways.

,In one convenient example ofthe invention, however,

in which the inner surface of thepiston crown .is domed (i. e. concave) or substantially flat it may be convenient to usean arrangementin which the oil is; ejected substantially wholly through"the central aperture. In this .case -it will be ,seen that the balance between the oil delivered and ejectedduring each reciprocation of the piston will be reached when the volume. of oil lying under the piston crown and immediately above the central opening at the end of each outstroke of the piston equals the volume of oiludeliyered by the nozzle through the central aperture during each reciprocation. In many casesit may not be desirable or convenient however to givethe underside ofthe .piston crown such ashape that the quantity of oil required to. be retained for cooling efficiency would be .so [retained if all the oil lying immediately above the central .aperture' at the end of each instroke of the .piston couldbe ejected .throughthe central aperture: during the succeeding outstroke.

Ina piston assembly according to the invention, therefore, the trough member may-include or carry a' baffle platelying'overpart of/or3the whole ofthe area ofthe central aperture and spaced from 'the inner edge of'the trough, so that the required'balance' between the oil delivered into and ejeeted fromf'the space between the trough and the piston crown will only be achieved when there is a quantity ofoillying on the side of thebaffie plate remote from the crown atthe end of each instroke of the piston. determining the quantity of oil which will .be retained The bafiieplate therefore is a factorin and shaken ba'ck and forth in the space between "the pistoncrown and the. trough and this quantity can be determinedin; accordance with requirements by giving to the ba'fiie plate a suitable shape anddisposition in relation to theinternal shape of the piston element.

Alternatively, andwhethersuch a bafile plate is provided or not, some of the ,oil may be .ejected through a space or spaces between the edge of the outer wall of the trough and theadjacent parts of the piston element,

of oil may take place "through one or more ejection passages eachof which opens into the trough "forlthis *purpose'at a point displaced from'the base of the trough and extends to a point within the skirt portion on the .side

of the trough remote from the crown, the arrangement being such that the volume of oil in the space between the trough and the crown during operation becomes stable when the oil ejectedthrou'gh the ejection passageor passages towards the end ofeach outstroke of the piston equals the quantity delivered into the space between the trough member and the crown during each complete reciprocation, less any oil which maybe ejected through the centralaperture and/ or between theedge ofthe outer wall of the trough'andthe piston body, where the construction is such as to provide for part ofthe oiltobe so ejected.

The troughmember will generally conveniently be of oblong or oval form" when viewedalong the pistonairis, @with .itsilonger axis extending at right angles .tolthe gudgeonpin axis, and with the central aperture, which is conviently Y of slot-like form, extending along (that longer axis.

Three constructions according 1 to the invention .are illustratedby wayof example in theaccompanying drawings in:which:

Figure 1: lista cross :sectiomthroughwne form" ofpiston according to the invention, the section being taken in a vertical plane containing the piston axis and at right angles to the gudgeon pin axis,

Figure 2 is a cross section of the piston shown in Figure 1 on the line 22 of Figure 1,

Figure 3 is a cross section on the line 3-3 of Figure 1,

Figure 4 is a similar view to Figure 1 of an alternative form of piston according to the invention, but with the gudgeon pin and connecting rod omitted,

Figure 5 is a cross section on the line 55 of Figure 4,

Figure 6 is a cross section on the line 66 of Figure 4,

Figure 7 is a similar view to Figure 3 showing a modification which may be used in some cases,

Figure 8 is a similar view to Figure 4 of a further form of piston according to the invention,

Figure 9 is a cross section on the line 9--9 of Figure 8,

Figure 10 is a cross section on the line 1010 of Figure 8, and

Figure 10a is a detailed fragmentary cross-section on the line 10a10a of Figure 10.

In the construction shown in Figures 1, 2 and 3, the piston assembly comprises piston body including a crown 1 from which projects downwards a ring-carrying portion 2 and a skirt portion 3 provided with gudgeon pin bosses 4. When the piston body is assembled in an engine it is connected by a gudgeon pin 5 to a connecting rod 6 containing an oil delivery passage 7 in known manner serving to supply oil to a nozzle 7* from which oil is ejected upwards towards the piston crown at least during the latter part of each upward stroke of the piston.

Secured to a pair of bosses or platforms 8 on the ringcarrying part 2 of the piston body is a self contained trough member of generally rectangular form in plan comprising a base 9 and inner and outer walls 10 and 11, the trough member being secured to the platforms 8 by means of bolts 12 passing through lugs 13 formed on the trough member as shown in Figures 1 and 3. The inner wall 10 of the trough member surrounds a central aperture 14 and has formed integral with it a bafile plate 15 supported from the wall 10 at two opposite sides by webs 16 so as to lie above the aperture 14, as shown clearly in Figure l. The longer sides of the Wall 11 of the trough member lie close to the inner flat faces 4 of the bosses 4 as shown in Figure 3 so that there is only a very narrow space between these longer sides and the faces 4*, while the dimensions of the platforms 8 are such in relation to the dimensions and form of the adjacent shorter sides of the outer wall 11 of the trough member that over a substantial length the upper edges of the shorter sides of the outer wall 11 make a rigid abutment with the platforms 8 as can be seen in Figure 3.

The aperture 14 not only provides the aperture from which oil ejected from the nozzle 7 enters the chamber 1 between the trough member of the piston crown 1 but also substantially the only exit passage for the escape of oil from such chamber.

The dimensions of the baffle 15 are such that it lies substantially completely over the opening 14 so that sub stantially no oil will be ejected through the aperture 14 at the end of each downstroke of the piston until the quantity of oil in the chamber 1 is such that, when this oil is retained against the underface of the piston crown 1 the lower surface of the oil lies below at least a part of the baffle 15.

During operation equilibrium will be reached approximately when the quantity of oil which lies between the underside of the baffle 15 and immediately over the opening 14 at the end of each upstroke and the beginning of each downstroke of the piston equals the quantity of oil which is delivered from the nozzle 7 into the chamber 1 during each up-piston stroke.

In the modified construction shown in Figures 4, 5 and 6 the construction of the piston body is approximately the same as that shown in Figures 1, 2 and 3 except that instead of gudgeon pin bosses of the form shown in Figures 1, 2 and 3 having the flat inner faces 4 of substantial area to lie close to the longer outer sides of the trough member, gudgeon pin bosses 17 of approximate- 1y circular form are employed and other consequential modifications to the piston body are provided as generally indicated in Figures 4, 5 and 6. In this construction the trough member is of the same general form as that shown in Figures 1, 2 and 3, and corresponding reference numerals have therefore been used for the corresponding parts thereof. In this construction however the baflle 15 lies somewhat nearer to the upper edge of the wall 10 forming the opening 14 and somewhat further from the crown 1 of the piston, and, as will be seen in Figures 5 and 6, the longer sides of the upper wall 11 of the trough are considerably spaced from the adjacent inner surface of the part 2 of the piston. The arrangement is, therefore, such that the trough formed by the base 9 and inner and outer walls 10 and 11 has a volume which is somewhat greater than the volume of the part of the chamber 1 which lies above the dotted line indicated at 18. In operation therefore the oil will build up in the chamber 1 until equilibrium is reached when the volume of oil in the chamber 1 becomes such that at the end of each downstroke of the piston the quantity ejected between the outer edges of the wall 11 of the trough and the inner surfaces of the part 2 of the piston as shown at 18 equals the quantity delivered into the chamber 1 from the nozzle during each upstroke of the piston.

In the modification shown in Figure 7 the piston body would be of approximately the same form as that shown in Figures 1, 2 and 3 with the trough member disposed approximately as shown in Figures 4, 5 and 6 in relation to the piston crown while the form of the trough member is modified as shown at 19 in Figure 7. Thus each of the longer sides of the trough member is of wide angle V form in plan so as to leave substantial spaces 20 between these longer sides and the flat inner faces 4 of the gudgeon pin bosses 4. During operation the ejection of oil to maintain equilibrium will take place between the longer sides 19 of the outer wall of the trough member and the fiat surfaces 4 With the modification shown in Figure 7 therefore the general form of the piston body as regards the gudgeon pin bosses can be the same as that shown in Figures 1, 2 and 3 while the trough member will operate in the manner described with reference to Figures 4, 5 and 6.

In the further modification shown in Figures 8, 9 and l0 the piston assembly is of the same general construction as that shown in Figures 4, 5 and 6 which, will not, therefore, again be described except for a modification to the gudgeon pin boss arrangement which provides for fiat inner faces 24 lying close to the longer sides of the outer wall of the trough member as will be clear from Figure 10.

In this construction the general dimensions of the trough member, including the height of the baffle member 15 above the upper edge of the inner wall 10 are the same as in Figures 4, 5 and 6 but the trough member is formed in two opposite corners with internal bosses as indicated at 21 the upper faces of which lie below the level of the upper edges of the inner and outer walls, 11 and 11 of the trough, each of these bosses being hollow and thus providing an exit passage 22 extending to below the bottom 9 of the trough.

It will be apparent that in this construction no substantial ejection of oil will take place through the opening 14 unless there is a volume of oil in the chamber 1 great enough substantially to overfill the trough. Equilibrium will be reached when, during the latter part of each downstroke of the piston, the level of the oil thrown into the trough is above the upper faces of the bosses 21 to an extent such that the volume of oil which otherwise would lie above the level of these upper faces approximately equals the volume of oil delivered duling each piston up stroke into the chamber 1 Ejection of oil therefore takes place substantially completely through the apertures 22 and it will be understood that if desired these may be directed and/or disposed so that the oil so ejected tends not to be ejected on to moving parts of the crankshaft assembly.

One of the advantages of the invention is that it facilitates manufacture since the piston body 1, 2, 3, can be of a form which can be pressed or diecast and the others die-cast and, apart from suitable platform surfaces or the like to which the trough member can be secured, need not have any special internal formation for the retention of oil. Greater freedom for the design of this piston body is, therefore, possible.

It may be possible in many applications in fact to employ a common form of piston body into which a trough member can be assembled when oil cooling of a piston according to the invention is desired or from which the trough member can be omitted and yet a satisfactory piston provided for engines in which oil cooling is not required.

Another advantage of the invention in some instances is that where, as usual and in the constructions shown in the drawings, it is desired to provide a groove for a scraper ring immediately below the grooves for the pressure retaining piston rings, with oil holes immediately below the scraper ring groove as indicated at 23 in Figure 1, the fact that the trough member is self contained enables this to be done without the complications which may arise with pistons as described in the U. S. Patent No. 2,523,699 mentioned above due to the fact that in such pistons the drain holes would be in a position in which oil which may be carried on the inner surface of the piston skirt during the instroke of the piston would by its inertia tend to enter the drain holes during the deceleration and subsequent reverse acceleration of the piston to the position of the integral Wall forming the base of the trough and thus prevent draining. Thus with pistons according to the present invention there is no necessity for an integral wall projecting radially inwards from the inner surface of the piston skirt to form the base of a trough, and the drain holes can thus safely enter the interior of the piston at any point below the edge of the outer wall of the trough member.

It will be understood that in piston assemblies according to the invention the trough may be made of the same material as the piston body or of diiferent material. Preferably, however, the trough member and the piston body will be made of materials having substantially the same thermal expansion the piston body and the trough mem-- 0 1. A trunk piston assembly for an internal combustion engine comprising a piston element including a crown, a ring-carrying portion projecting from the crown and a skirt portion integnal with the ring-carrying portion and provided with gudgeon pin bosses, and a unitary detachable trough member secured within the piston element so as to be spaced from the crown and lie above the gudgeon pin bosses, which trough member is of annular form and comprises an annular base and inner and outer side walls projecting from the base towards the crown to provide a trough which will retain a quantity of oil and surrounds an aperture, through which oil can be fed into the space between the trough and the crown from a nozzle on the connecting rod.

2. A trunk piston assembly as claimed in claim 1 in which the self-contained trough member includes a baflie plate lying over at least part of the area of the aperture which is surrounded by the edge of the inner wall of the trough, said plate being spaced from such edge.

3. A tr-unk piston assembly as claimed in claim 2 in which the battle is supported from the edge of the inner wall of the trough member by parts projecting from such inner wall and situated at the opposite sides of the trough which lie adjacent to the gudgeon pin bosses.

4. A trunk piston assembly as claimed in claim 3 in which the outer side wall of the trough is spaced for part of its length at least from the adjacent parts of the piston element.

5. A trunk piston assembly as claimed in claim 2 in which the outer side wall is spaced for part of its length at least from the adjacent part of the piston element.

6. A trunk piston assembly as claimed in claim 1 in which the trough is of generally oblong shape viewed along the axis of the piston, and has a similarly elongated aperture.

7. A trunk piston assembly as claimed in claim 2 in which at least part of the outer wall of the trough memher is spaced from the adjacent part of the piston element.

8. A trunk piston assembly as claimed in claim 1 in which the trough member has at least one oil discharge aperture the upper end of which opens into the trough at a point below the level of the upper edge of said trough while its lower end opens through the base of the trough.

References Cited in the file of this patent UNITED STATES PATENTS 2,372,050 Barraja-Frauenfelder et a1. Mar. 20, 1945 2,523,699 I-Iolt et a1. Sept. 26, 1950 FOREIGN PATENTS 666,195 Great Britain Feb. 6, 1952 

